U.S. patent application number 16/344621 was filed with the patent office on 2020-02-27 for dielectric-heating bonding film and joining method using dielectric-heating bonding film.
This patent application is currently assigned to LINTEC Corporation. The applicant listed for this patent is LINTEC CORPORATION. Invention is credited to Masakazu ISHIKAWA, Tatsuya IZUMI.
Application Number | 20200063001 16/344621 |
Document ID | / |
Family ID | 62023521 |
Filed Date | 2020-02-27 |
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United States Patent
Application |
20200063001 |
Kind Code |
A1 |
ISHIKAWA; Masakazu ; et
al. |
February 27, 2020 |
DIELECTRIC-HEATING BONDING FILM AND JOINING METHOD USING
DIELECTRIC-HEATING BONDING FILM
Abstract
A dielectric welding film capable of tightly welding adherends
of a polyolefin resin or the like within a relatively short time
through dielectric heating, and a bonding method using the
dielectric welding film are provided. The dielectric welding film
is configured to bond a plurality of adherends of the same material
or different materials through dielectric heating, the dielectric
welding film containing (A) a polyolefin resin and (B) a dielectric
filler whose mean particle size measured in accordance with JIS Z
8819-2 (2001) is in a range from 1 to 30 .mu.m, a thickness of the
dielectric welding film ranging from 10 to 2,000 .mu.m. The method
uses the dielectric welding film.
Inventors: |
ISHIKAWA; Masakazu; (Tokyo,
JP) ; IZUMI; Tatsuya; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LINTEC CORPORATION |
Tokyo |
|
JP |
|
|
Assignee: |
LINTEC Corporation
Tokyo
JP
|
Family ID: |
62023521 |
Appl. No.: |
16/344621 |
Filed: |
October 18, 2017 |
PCT Filed: |
October 18, 2017 |
PCT NO: |
PCT/JP2017/037616 |
371 Date: |
April 24, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08K 3/22 20130101; C09J
177/00 20130101; H01B 17/56 20130101; C08K 2003/2237 20130101; B29C
65/50 20130101; C09J 2205/30 20130101; C09J 125/04 20130101; C08K
2201/005 20130101; C09J 2423/106 20130101; H01B 3/441 20130101;
B23K 13/00 20130101; C09J 11/04 20130101; C09J 2423/10 20130101;
C09J 2205/102 20130101; C09J 2467/00 20130101; C09J 9/00 20130101;
C09J 123/00 20130101; C08K 3/14 20130101; C09J 123/26 20130101;
C09J 2203/326 20130101; C09J 201/00 20130101; C09J 2423/00
20130101; C09J 7/00 20130101; B29C 65/40 20130101; H05B 6/50
20130101; C09J 7/10 20180101; C09J 129/14 20130101; C09J 167/00
20130101; B29C 65/04 20130101; C09J 7/35 20180101; C09J 131/04
20130101; H05B 6/64 20130101; C08K 2003/2296 20130101; B29C 65/425
20130101; C09J 2301/416 20200801; H05B 6/46 20130101; C09J 2301/408
20200801; C09J 5/06 20130101; C09J 123/10 20130101; C09J 2201/61
20130101 |
International
Class: |
C09J 11/04 20060101
C09J011/04; C09J 9/00 20060101 C09J009/00; C09J 7/35 20060101
C09J007/35; C09J 5/06 20060101 C09J005/06; B29C 65/04 20060101
B29C065/04; B29C 65/42 20060101 B29C065/42; H01B 3/44 20060101
H01B003/44; H01B 17/56 20060101 H01B017/56; H05B 6/50 20060101
H05B006/50 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 27, 2016 |
JP |
2016-210218 |
Feb 9, 2017 |
JP |
2017-021803 |
Feb 9, 2017 |
JP |
2017-021806 |
Claims
1. A dielectric welding film configured to bond a plurality of
adherends of the same material or different materials though
dielectric heating, the dielectric welding film comprising: (A) a
polyolefin resin; and (B) a dielectric filler whose mean particle
size measured in accordance with JIS Z 8819-2 (2001) is in a range
from 2 to 50 .mu.m, wherein the dielectric filler is zinc oxide,
anatase-type titanium oxide or barium titanate, and a thickness of
the dielectric welding film is in a range from 100 to 1000
.mu.m.
2. The dielectric welding film according to claim 1, wherein a
content of the (B) component is in a range from 5 to 800 parts by
weight with respect to 100 parts by weight of the (A)
component.
3. The dielectric welding film according to claim 1, wherein the
(A) component is a polypropylene resin.
4. The dielectric welding film according to claim 3, wherein a
melting point or a softening point of the polypropylene resin as
the (A) component defined in accordance with JIS K 7121 (1987) is
in a range from 80 to 200 degrees C.
5. (canceled)
6. The dielectric welding film according to claim 1, wherein a
dielectric property (tan .delta./.epsilon.') defined by dividing a
dissipation factor tan .delta. by a permittivity .epsilon.' at 23
degrees C. and 40 MHz frequency is 0.005 or more.
7. The dielectric welding film according to claim 1, wherein a
storage modulus E' measured at 23 degrees C. and 10 Hz frequency
and a storage modulus E' measured at 80 degrees C. and 10 Hz
frequency are both in a range from 1.times.10.sup.6 to
1.times.10.sup.10 Pa.
8. A bonding method using a dielectric welding film configured to
bond a plurality of adherends of the same material or different
materials through dielectric heating, the dielectric welding film
comprising (A) a polyolefin resin and (B) a dielectric filler whose
mean particle size measured in accordance with JIS Z 8819-2 (2001)
is in a range from 2 to 25 .mu.m, the dielectric filler being zinc
oxide, anatase-type titanium oxide or barium titanate, a thickness
of the dielectric welding film ranging from 100 to 1000 .mu.m, the
method comprising: (1) holding the dielectric welding film between
the plurality of adherends of the same material or different
materials; and (2) applying the dielectric heating on the
dielectric welding film held between the plurality of adherends
with a dielectric heater at a frequency ranging from 1 to 100
MHz.
9. The dielectric welding film according to claim 1, wherein the
(B) component is zinc oxide.
10. The dielectric welding film according to claim 1, wherein a
light transmissivity of the dielectric welding film is 5% or
more.
11. The bonding method using a dielectric welding film according to
claim 8, wherein the (B) component is zinc oxide.
12. The bonding method using a dielectric welding film according to
claim 8, wherein a high frequency is applied in (2) applying the
dielectric heating at a high-frequency output ranging from 0.1 to
20 kW and a high-frequency-wave application time of 1 second or
more and less than 40 seconds.
Description
TECHNICAL FIELD
[0001] The present invention relates to a dielectric welding film,
and a bonding method using the dielectric welding film.
[0002] Specifically, the present invention relates to a dielectric
welding film, which is usable for a typically hard-to-bond adherend
and is capable of providing a large bonding force through a
relatively short period of dielectric heating (sometimes referred
to as high-frequency dielectric heating hereinafter), and a bonding
method using the dielectric welding film.
BACKGROUND ART
[0003] In order to bond a plurality of typically hard-to-bond
adherends (i.e. difficult to be bonded), it has been recently
proposed that, for instance, a bonding process such as dielectric
heating, induction heating, ultrasonic welding or laser welding is
performed with an adhesive produced by blending a heat-generating
material in a predetermined resin.
[0004] According to a proposed bonding method by dielectric heating
among the above, an adhesive blended with carbon black (CB),
silicon carbide (SiC), or the like is interposed between a
plurality of adherends and dielectric heating at a frequency of 28
or 40 MHz or microwave heating is applied to bond the plurality of
adherends (see Patent Literatures 1 and 2).
[0005] According to another proposed bonding method by dielectric
heating, polyolefin resin is blended with a ferroelectric material
and a carbon compound or a conductive material to prepare an
adhesive with a dissipation factor (tan .delta.) of 0.03 or more,
and the adhesive is interposed between a plurality of adherends to
weld the adherends through dielectric heating at a frequency of 40
MHz (see Patent Literatures 3 and 4).
[0006] According to still another proposed related art, an adhesive
composition for dielectric heating is produced by adding a
dielectric heating medium to an adhesive compatible with a
plurality of adherends (base materials) to be bonded. The adhesion
layer composition for dielectric heating satisfies a formula:
C.times.{(tan .delta.)/.epsilon.'}1/2.gtoreq.d, where .epsilon.'
represents specific permittivity, tan .delta. represents a
dissipation factor, d (mm) represents a total thickness of the base
materials to be bonded, and the coefficient C is in a range from 78
to 85 (see Patent Literature 5).
CITATION LIST
Patent Literature(s)
TABLE-US-00001 [0007] Patent Literature 1 JP 2010-6908 A (claims
etc.) Patent Literature 2 JP 2008-156510 A (claims etc.) Patent
Literature 3 JP 2003-238745 A (claims etc.) Patent Literature 4 JP
2003-193009 A (claims etc.) Patent Literature 5 JP 2014-37489 A
(claims etc.)
SUMMARY OF THE INVENTION
Problem(s) to be Solved by the Invention
[0008] However, the dielectric heating process disclosed in Patent
Literature 1 or 2, in which a considerable amount of the conductive
material such as carbon black (CB) is blended in the adhesive to
prepare the adhesion layer composition, is likely to cause electric
breakdown during the dielectric heating to carbonize a bonded
portion and/or the adherends.
[0009] In addition, vertical alignment of the adherends is
difficult due to the color of the resultant adhesion layer
composition (i.e. perfectly opaque black (visible light
transmissivity: 0%)), so that it is difficult to apply the
dielectric heating at an accurate position.
[0010] The dielectric heating process disclosed in Patent
Literature 3 or 4 is also likely to cause electric breakdown during
the dielectric heating due to a considerable amount of the
conductive material (e.g. metal and carbide compound) added in the
adhesive resin composition.
[0011] In addition, vertical alignment of the adherends is also
difficult because of poor transparency of the resultant adhesive
resin composition (i.e. perfectly opaque (visible light
transmissivity: 0%)), so that it is difficult to apply the
dielectric heating at an accurate position.
[0012] According to the adhesion layer composition for dielectric
heating disclosed in Patent Literature 5, the types of usable
adherends are likely to be extremely limited.
[0013] In addition, in order to ensure sufficient bonding strength,
dielectric heating has to be applied for at least 40 to 70 seconds,
which is considerably long in terms of practical use.
[0014] In view of the above, the inventors have found through
dedicated studies that excellent bondability of a plurality of
typically hard-to-bond adherends (i.e. irrespective of the type of
the adherends) can be obtained even with a polyolefin-resin-based
welding film through, for instance, dielectric heating of less than
40 seconds, as long as a mean particle size (median diameter: D50)
of the contained dielectric filler is controlled. The invention has
been made based on the above findings.
[0015] An object of the invention is to provide a dielectric
heating adhesive including a combination of a predetermined resin
and a predetermined dielectric filler capable of preventing
occurrence of electric breakdown and tightly bonding typically
hard-to-bond adherends within an extremely short time, and to
provide a bonding method using a predetermined dielectric welding
film.
Means for Solving the Problems
[0016] A dielectric welding film according to an aspect of the
invention is configured to bond a plurality of adherends of the
same material or different materials though dielectric heating, the
dielectric welding film including:
[0017] (A) a polyolefin resin; and
[0018] (B) a dielectric filler whose mean particle size measured in
accordance with JIS Z 8819-2 (2001) is in a range from 1 to 30
.mu.m, in which
[0019] a thickness of the dielectric welding film is in a range
from 10 to 2000 .mu.m. The above-described problems can be solved
by the dielectric welding film.
[0020] The dielectric welding film according to the above aspect of
the invention provides excellent bondability through dielectric
heating of, for instance, less than 40 seconds irrespective of the
type of the adherends.
[0021] In the dielectric welding film according to the above aspect
of the invention, the content of the (B) component is preferably in
a range from 5 to 800 parts by weight with respect to 100 parts by
weight the (A) component.
[0022] At the dielectric content of the (B) component, excellent
bondability can be obtained through a relatively short period of
dielectric heating irrespective of the type of the adherends.
[0023] In the dielectric welding film according to the above aspect
of the invention, the (A) component is preferably a polypropylene
resin whose melting point or softening point is in a range from 80
to 200 degrees C.
[0024] The (A) component (i.e. the polypropylene resin) having the
above melting point or softening point can achieve an excellent
balance between heat resistance in a use environment and
weldability during the dielectric heating.
[0025] In the dielectric welding film according to the above aspect
of the invention, the (B) component is preferably zinc oxide.
[0026] The (B) component in a form of zinc oxide can exhibit a
predetermined exothermic effect during the dielectric heating even
in a relatively small amount.
[0027] In the dielectric welding film according to the above aspect
of the invention, a dielectric property (tan .delta./.epsilon.')
defined by dividing a dissipation factor tan .delta. by a
permittivity .epsilon.' at 23 degrees C. and 40 MHz frequency is
preferably 0.005 or more.
[0028] By controlling the above value of the dielectric property,
excellent weldability during the dielectric heating can be ensured
and, consequently, a plurality of adherends can be tightly
bonded.
[0029] In the dielectric welding film according to the above aspect
of the invention, a storage modulus E' measured at 80 degrees C.
and 10 Hz frequency are preferably both in a range from
1.times.10.sup.6 to 1.times.10.sup.10 Pa.
[0030] By controlling the storage modulus E' measured under the
predetermined conditions, predetermined handleability as the
dielectric welding film can be ensured, the dielectric welding film
can be wound into an elongated roll, and the dielectric welding
film is relatively easily applicable to a roll-to-roll process.
[0031] A bonding method according to another aspect of the
invention uses a dielectric welding film configured to bond a
plurality of adherends of the same material or different materials
through dielectric heating, the dielectric welding film including
(A) a polyolefin resin and (B) a dielectric filler whose mean
particle size measured in accordance with JIS Z 8819-2 (2001) is in
a range from 1 to 30 .mu.m, a thickness of the dielectric welding
film ranging from 10 to 2000 .mu.m, the method including:
(1) holding the dielectric welding film between the plurality of
adherends of the same material or different materials; and (2)
applying the dielectric heating on the dielectric welding film held
between the plurality of adherends with a dielectric heater at a
high-frequency output ranging from 0.1 to 20 kW and a
high-frequency-wave application time of 1 second or more and less
than 40 seconds.
[0032] The dielectric welding film according to the above aspect of
the invention provides excellent bondability through a relatively
short period of dielectric heating time of, for instance, less than
40 seconds irrespective of the type of the adherends.
BRIEF DESCRIPTION OF DRAWING(S)
[0033] FIG. 1 illustrates an influence of a melting point or a
softening point of a (A) component (polyolefin resin) on a
high-temperature creep test.
[0034] FIG. 2 illustrates an influence of a mean particle size of a
(B) component (dielectric filler) on high-frequency weldability of
a dielectric welding film.
[0035] FIG. 3 illustrates an influence of a mean particle size of
the (B) component (dielectric filler) on dielectric property (tan
.delta./.epsilon.').
[0036] FIG. 4 illustrates an effect of the type (6 types) and
content (3 levels) of the (B) component (dielectric filler) on the
dielectric property (tan .delta./.epsilon.').
[0037] FIG. 5 illustrates dielectric heating performed by a
dielectric heater.
[0038] FIGS. 6 (a) and (b) are photographs showing a surface of the
dielectric welding film and a cross section of the dielectric
welding film according to an exemplary embodiment of the invention
(1000.times. magnification).
DESCRIPTION OF EMBODIMENT(S)
First Exemplary Embodiment
[0039] A dielectric welding film according to a first exemplary
embodiment is configured to weld adherends of the same material or
different materials though dielectric heating, the dielectric
welding film including:
[0040] (A) a polyolefin resin; and
[0041] (B) a dielectric filler whose mean particle size (D50)
measured in accordance with JIS Z 8819-2 (2001) is in a range from
1 to 30 .mu.m,
[0042] a thickness of the dielectric welding film ranging from 10
to 2000 .mu.m.
[0043] The components, properties, and the like of the dielectric
welding film according to the first exemplary embodiment will be
specifically described below.
1 Components of Dielectric Welding Film
(1)(A) Component: Polyolefin Resin
Type
[0044] Examples of the polyolefin resin (main component), the type
of which is not limited, include homopolymer resins such as
polyethylene, polypropylene, polybutene, and polymethylpentene, and
.alpha.-olefin resins of copolymers of ethylene, propylene, butene,
hexene, octene, 4-methylpentene, and the like. The polyolefin resin
may consist of a single one of the resins above, or may be a
combination of two or more thereof. Among the polyolefin resins,
polypropylene resin is especially preferable in terms of its
excellent mechanical strength and stable welding properties.
Melting Point Or Softening Point
[0045] The melting point or softening point of the polyolefin resin
is preferably in a range from 80 to 200 degrees C.
[0046] Specifically, a crystalline polyolefin resin, whose melting
point (i.e. a temperature at which a crystalline portion is melted)
measured by a differential scanning calorimeter (DSC) or the like
is defined within a predetermined range, can achieve a good balance
between heat resistance in a use environment and the like and
weldability during the dielectric heating.
[0047] More specifically, the melting point may be determined using
a differential scanning calorimeter (DSC) by: raising a temperature
of a 10-mg measurement sample (crystalline polyolefin resin) to 250
degrees C.; cooling the measurement sample to 25 degrees C. at a
temperature-decrease rate of 10 degrees C./min to crystallize the
measurement sample; again heating the measurement sample at a
temperature-increase rate of 10 degrees C./min to re-melt the
sample; and measuring a peak temperature (melting point) of a
melting peak observed on a DSC chart (fusion curve) when the sample
is re-melted.
[0048] An amorphous polyolefin resin, whose softening point (glass
transition point) (i.e. a temperature at which an amorphous portion
is melted) measured in accordance with a ring-and-ball method or
the like is defined within a predetermined range, can also achieve
a good balance between heat resistance and weldability during the
dielectric heating.
[0049] More specifically, the softening point of the amorphous
polyolefin resin can be measured in accordance with JIS K 6863
(1994).
[0050] In either case, when the melting point of the crystalline
polyolefin resin or the softening point of the amorphous polyolefin
resin falls below 80 degrees C., the heat resistance may become so
insufficient that the applicable range may be extremely limited
and/or mechanical strength may be significantly reduced.
[0051] In contrast, when the melting point of the crystalline
polyolefin resin or the softening point of the amorphous polyolefin
resin exceeds 200 degrees C., welding through the dielectric
heating may take extremely long time and/or the bonding strength
may be extremely decreased.
[0052] The melting point or the softening point of the dielectric
welding film of the first exemplary embodiment, which may either a
crystalline polyolefin resin or an amorphous polyolefin resin, more
preferably ranges from 100 to 190 degrees C., further preferably
from 130 to 180 degrees C.
[0053] A relationship between the melting point or the softening
point of the (A) component and a high-temperature creep test will
be described below with reference to FIG. 1.
[0054] An abscissa axis of FIG. 1 represents the melting point or
the softening point of the (A) component (degrees C.). An ordinate
axis of FIG. 1 represents a result of the high-temperature creep
test (relative evaluation). More specifically, the relative
evaluation was done as an evaluation of Example 1 below, where the
mark .circleincircle. was rated as 5 points, the mark .largecircle.
was rated as 3 points, the mark .DELTA. was rated as 1 point, and
the mark x was rated as 0 points.
[0055] As can be understood from the characteristic curve in FIG.
1, when the melting point or the like of the (A) component is as
low as approximately 70 degrees C., the score of the relative
evaluation of the result of the high-temperature creep test tends
to be low, whereas the score of the relative evaluation tends to
improve with an increase in the melting point or the like.
[0056] More specifically, when the melting point or the like of the
(A) component is 130 degrees C. or more, 3 or more scores of the
evaluation value can be obtained in the high-temperature creep
test.
[0057] Accordingly, it is found that the melting point or the like
of the (A) component is preferably in a range from, for instance,
120 to 200 degrees C. based only on the results of the
high-temperature creep test.
Average Molecular Weight
[0058] The average molecular weight (weight average molecular
weight) of the polyolefin resin is usually preferably in a range
from 5000 to 300000.
[0059] This is because, when the weight average molecular weight of
the polyolefin resin falls below 5000, the heat resistance and/or
the bonding strength may be significantly reduced.
[0060] In contrast, when the weight average molecular weight of the
polyolefin resin exceeds 300000, the weldability and the like
resulting from the dielectric heating may be significantly
reduced.
[0061] The weight average molecular weight of the polyolefin resin
is thus more preferably in a range from 10000 to 200000, further
preferably from 30000 to 100000.
[0062] It should be noted that the weight average molecular weight
of the polyolefin resin can be measured through, for instance, an
intrinsic viscosity method in accordance with JIS K 7367-3
(1999).
[0063] The melt flow rate (MFR) of the polyolefin resin is usually
preferably in a range from 1 to 300 g/10 min at 230 degrees C.
under 2.16 kg load. When the MFR is 1 g/10 min or more, the heat
resistance at the welded portion is improved. Further, when the MFR
is 300 g/10 min or less, the bonding time through the dielectric
heating can be reduced, resulting in stable welding properties.
[0064] The MFR of the polyolefin resin is thus more preferably in a
range from 1 to 100 g/10 min, further preferably from 1 to 50 g/10
min. It should be noted that the MFR of the polyolefin resin can be
measured at 230 degrees C. under 2.16 kg load in accordance with
JIS K 7210-1 (2014).
(2) B Component: Dielectric Filler
Type
[0065] The dielectric filler (main component) is a
high-frequency-wave absorbing filler having a high dielectric loss
factor enough to generate heat when a high-frequency wave of, for
instance, 28 MHz or 40 MHz frequency is applied.
[0066] Such a dielectric filler is preferably a single one of or a
combination of two or more of compounds selected from zinc oxide,
silicon carbide (SiC), anatase-type titanium oxide, barium
titanate, barium zirconate titanate, lead titanate, potassium
niobate, rutile-type titanium oxide, hydrated aluminum silicate,
inorganic substance having crystallization water such as hydrated
aluminosilicate salt of alkali metal or alkaline earth metal, and
the like. Among the above, zinc oxide, which includes various
types, provides wide selection of shapes and sizes, and allows
modification of welding and mechanical properties of the dielectric
welding film in accordance with the intended use, is especially
preferable as the dielectric filler.
Content
[0067] The content of the (B) component is preferably in a range
from 5 to 800 parts by weight with respect to 100 parts by weight
of the (A) component.
[0068] This is because, when the content of the (B) component
becomes excessively small, heat-generating performance may become
poor, so that the (A) component may be less likely to be melted,
failing to provide strong bonding after the dielectric heating.
[0069] In contrast, when the content of the (B) component becomes
excessively large, fluidity of the dielectric welding film during
the dielectric heating may be excessively reduced.
[0070] The content of the (B) component is thus preferably in a
range from 30 to 600 parts by weight with respect to 100 parts by
weight of the (A) component, more preferably in a range from 50 to
300 parts by weight.
Mean Particle Size
[0071] A mean particle size (median diameter: D50) of the (B)
component measured in accordance with JIS Z 8819-2 (2001) is in a
range from 1 to 30 .mu.m.
[0072] This is because, when the mean particle size is less than 1
.mu.m, the filler is less polarized because of the reduction in the
polarizable distance inside the filler to reduce inversion motion
caused when a high-frequency wave is applied, so that the
dielectric heating performance may be too decreased to tightly bond
the adherends.
[0073] In contrast, as the mean particle size increases, the filler
is more polarized because of the increase in the polarizable
distance inside the filler, so that the inversion motion caused
when a high-frequency wave is applied is intensified, thereby
improving the dielectric heating performance.
[0074] However, when the mean particle size exceeds 30 .mu.m, the
distance between neighboring dielectric fillers becomes short and
the inversion motion caused when a high-frequency wave is applied
is attenuated under the influence of an electric charge of the
neighboring dielectric fillers, so that the dielectric heating
performance may be too decreased to tightly weld the adherends.
[0075] The mean particle size of the (B) component is thus more
preferably in a range from 2 to 25 .mu.m, further preferably from 3
to 20 .mu.m.
[0076] A relationship between the mean particle size of the (B)
component and high-frequency weldability when the dielectric
welding film.
is used will be described below with reference to FIG. 2.
[0077] An abscissa axis of FIG. 2 represents the mean particle size
of the (B) component (.mu.m). An ordinate axis of FIG. 2 represents
a value of welding strength (relative evaluation). More
specifically, the relative evaluation was done as an evaluation of
Example 1 below, where the mark .circleincircle. was rated as 5
points, the mark .largecircle. was rated as 3 points, the mark
.DELTA. was rated as 1 point, and the mark x was rated as 0
points.
[0078] As can be understood from the characteristic curve in FIG.
2, there is an optimum value of the mean particle size of the (B)
component for the welding strength.
[0079] Specifically, when the mean particle size of the (B)
component is excessively small (e.g. 0.4 .mu.m), the adherends
cannot be sufficiently welded by applying the high-frequency
wave.
[0080] In contrast, when the mean particle size of the (B)
component becomes relatively large (e.g. 2 .mu.m), the evaluation
of the high-frequency weldability rapidly improves.
[0081] Further, when the mean particle size of the (B) component
becomes considerably large (e.g. 10 to 20 .mu.m), the evaluation of
the high-frequency weldability is substantially stabilized and is
improved as compared with the (B) component of excessively small
mean particle size.
[0082] In contrast, when the mean particle size of the (B)
component exceeds 40 .mu.m (e.g. 50 .mu.m), the evaluation of the
high-frequency weldability is reduced, instead of being improved,
to a level substantially the same as that of the excessively small
mean particle size.
[0083] Thus, there is an optimal value in the mean particle size of
the (B) component for the high-frequency weldability with the
dielectric welding film. For instance, the mean particle size is
more preferably in a range from 1 to 30 .mu.m, further preferably
from 2 to 20 .mu.m.
[0084] A relationship between the mean particle size of the (B)
component and dielectric property represented by tan
.delta./.epsilon.' will be described below with reference to FIG.
3.
[0085] An abscissa axis of FIG. 3 represents the mean particle size
of the (B) component (.mu.m). An ordinate axis of FIG. 3 represents
dielectric property represented by a value of tan
.delta./.epsilon.'.times.10.sup.-3.
[0086] As can be understood from the characteristic curve in FIG.
3, there is an optimum value of the mean particle size of the (B)
component for the dielectric property.
[0087] Specifically, when the mean particle size of the (B)
component is excessively small (e.g. 0.4 .mu.m), the dielectric
property is so low that it is estimated that adherends cannot be
sufficiently welded by applying the high-frequency wave.
[0088] In contrast, when the mean particle size of the (B)
component is relatively large (e.g. 2 .mu.m), the value of the
dielectric property rapidly improves to exceed 0.005 at least.
[0089] Further, when the mean particle size of the (B) component is
approximately 10 .mu.m, the value of the dielectric property is,
though slightly fluctuates, at least in a range from 0.008 to
0.01.
[0090] In contrast, when the mean particle size of the (B)
component exceeds 10 .mu.m to be approximately 20 .mu.m, the
evaluation of the dielectric property is reduced to fall below
0.008.
[0091] Further, when the mean particle size of the (B) component
exceeds 40 .mu.m to be approximately 50 .mu.m, the evaluation of
the dielectric property is considerably reduced (less than
0.002).
[0092] Thus, there is an optimal value in the mean particle size of
the (B) component for the dielectric property represented by tan
.delta./.epsilon.'. In order to achieve a relatively high value,
the mean particle size is, for instance, more preferably in a range
from 1 to 20 .mu.m, further preferably from 2 to 15 .mu.m.
[0093] A relationship between the types (total 6) and contents (3
levels) of the (B) component and the dielectric property
represented by tan .delta./.epsilon.' will be described below with
reference to FIG. 4.
[0094] An abscissa axis of FIG. 4 represents the content of the (B)
component (parts by weight) with respect to 100 parts by weight of
the (A) component. An ordinate axis of FIG. 4 represents a value of
the dielectric property represented by tan .delta./.epsilon.'.
[0095] It should be noted that a characteristic curve A corresponds
to TiO.sub.2 (anatase-type crystal), a characteristic curve B
corresponds to ZnO, a characteristic curve C corresponds to SiC, a
characteristic curve D corresponds to TiO.sub.2 (rutile-type
crystal), a characteristic curve E corresponds to BaTiO.sub.3, and
a characteristic curve F corresponds to ZrO.sub.2.
[0096] As can be understood from the characteristic curves A to C
in FIG. 4, when the (B) component is TiO.sub.2 (anatase-type
crystal), ZnO, or SiC, the value of the dielectric property (tan
.delta./.epsilon.') considerably increases with an increase in the
content of the (B) component to approximately 150 parts by
weight.
[0097] Further, as can be understood from the characteristic curves
A to C in FIG. 4, when the content increases to approximately 350
parts by weight, the value of the dielectric property (tan
.delta./.epsilon.') further increases, although seemingly partially
saturated.
[0098] In contrast, as can be understood from the characteristic
curves D to F, when the (B) component is TiO.sub.2 (rutile-type
crystal), BaTiO.sub.3, or ZrO.sub.2, the value of the dielectric
property (tan .delta./.epsilon.') is substantially unchanged
irrespective of an increase in the content of the (B) component to
approximately 150 parts by weight.
[0099] Thus, the type and content of the (B) component have a
strong impact on the dielectric property represented by tan
.delta./.epsilon.'. In order to achieve a relatively high value,
the content of the (B) component is more preferably, for instance,
in a range from 50 to 500 parts by weight with respect to 100 parts
by weight of the (A) component, further preferably from 100 to 400
parts by weight.
(3) Additive
[0100] The dielectric welding film is preferably added with at
least one of additives such as tackifier, plasticizer, wax,
coloring agent, antioxidant, ultraviolet absorber, antibacterial
agent, coupling agent, viscosity modifier, and organic or inorganic
filler other than the dielectric filler.
[0101] The tackifier and the plasticizer can improve melting and
welding properties of the dielectric welding film. Examples of the
tackifier include rosin derivative, polyterpene resin, aromatic
modified terpene resin and hydrogenated products thereof, terpene
phenol resin, coumarone indene resin, aliphatic petroleum resin,
and aromatic petroleum resin and hydrogenated products thereof.
Examples of the plasticizer include petroleum process oil such as
paraffin process oil, naphthene process oil and aromatic process
oil, natural oil such as castor oil and tall oil, and
low-molecular-weight liquid polymer such as diacid dialkyl (e.g.
dibutyl phthate, dioctyl phthate, and dibutyl adipate), liquid
polybutene and liquid polyisoprene.
[0102] When the additive is added, the content of the additive is
typically preferably in a range from 0.1 to 20 wt % of a total
amount of the dielectric welding film, more preferably in a range
from 1 to 10 wt %, further preferably in a range from 2 to 5 wt %,
though depending on the type and purpose of the additive.
2 Properties of Dielectric Welding Film
(1) Thickness
[0103] The thickness of the dielectric welding film is in a range
from 10 to 2000 .mu.m.
[0104] This is because, when the thickness of the dielectric
welding film is 10 .mu.m, the bonding strength between the
adherends sometimes rapidly decreases.
[0105] Meanwhile, when the thickness of the dielectric welding film
exceeds 2000 .mu.m, it is sometimes difficult to wind the
dielectric welding film into a roll and to apply the dielectric
welding film to a roll-to-roll process.
[0106] Accordingly, the thickness of the dielectric welding film is
typically more preferably in a range from 100 to 1000 .mu.m,
further preferably in a range from 200 to 600 .mu.m, though
depending on the usage of the dielectric welding film and the
like.
(2) Dielectric Property (Tan .delta./.epsilon.')
[0107] With regard to the properties of the dielectric welding
film, it is preferable that dielectric property (tan
.delta./.epsilon.'), which is represented by a dissipation factor
tan .delta. measured at 23 degrees C. and 40 MHz frequency and
permittivity .epsilon.' measured in the same manner, is 0.005 or
more.
[0108] This is because, when the dielectric property (tan
.delta./.epsilon.') is less than 0.005, the dielectric welding film
does not generate heat as desired through the dielectric heating
irrespective of the type of the polyolefin resin and the like,
sometimes making it difficult to tightly bond the adherends.
[0109] However, when the value of the dielectric property (tan
.delta./.epsilon.') becomes excessively large, it sometimes occurs
that the types of usable polyolefin resin and dielectric filler are
excessively limited and/or total light transmissivity is rapidly
reduced.
[0110] Accordingly, the dielectric property (tan
.delta./.epsilon.') of the dielectric welding film is more
preferably in a range from 0.008 to 0.05, further preferably in a
range from 0.01 to 0.03.
[0111] It should be noted that the measurement method of the
dielectric property (tan .delta./.epsilon.') of the dielectric
welding film will be detailed below in later-described Example
1.
(3) Light Transmissivity
[0112] Total light transmissivity of the dielectric welding film is
preferably 1% or more, more preferably 5% or more, further
preferably 10% or more.
[0113] This is because, when the total light transmissivity (%) is
less than 1%, it may become virtually difficult to visually locate
the dielectric welding film of an excessive thickness at a
predetermined point using transmitted light or the like. The upper
limit of the light transmissivity of the dielectric welding film,
which is not specifically limited, is usually approximately 50%
depending on a preferable blend ratio of the polyolefin resin and
the dielectric filler and the like.
[0114] It should be noted that the measurement method of the total
light transmissivity (%) of the dielectric welding film will be
detailed below in later-described Example 1.
(4) Viscoelastic Property
[0115] With regard to viscoelastic property (dynamic elastic
modulus) of the dielectric welding film, it is preferable that
storage modulus E' measured at 10 Hz frequency is in a range from
1.times.10.sup.6 to 1.times.10.sup.10 Pa both at a room temperature
and at 80 degrees C.
[0116] This is because, when the storage modulus E' is less than
1.times.10.sup.6 Pa at a room temperature or at 80 degrees C., the
surface of the dielectric welding film may become tacky to cause
blocking, which makes it difficult to store the dielectric welding
film in a roll.
[0117] Meanwhile, when the storage modulus E' exceeds
1.times.10.sup.10 Pa at a room temperature or at 80 degrees C., the
dielectric welding film may become brittle to make it difficult to
unroll the dielectric welding film or adhere the dielectric welding
film on an adherend while applying a high tension.
[0118] Accordingly, the storage modulus E' of the dielectric
welding film is more preferably in a range from 5.times.10.sup.6 Pa
to 5.times.10.sup.9 Pa at a room temperature and at 80 degrees C.,
further preferably in a range from 1.times.10.sup.7 Pa to
1.times.10.sup.9 Pa.
[0119] It should be noted that the measurement method of the
storage modulus E' of the dielectric welding film will be detailed
below in later-described Example 1.
Second Exemplary Embodiment
[0120] In a second exemplary embodiment, a bonding method using a
dielectric welding film for welding adherends of the same material
or different materials though dielectric heating will be
described.
[0121] The dielectric welding film includes (A) a polyolefin resin
and (B) a dielectric filler whose mean particle size measured in
accordance with JIS Z 8819-2 (2001) is in a range from 1 to 30
.mu.m. The thickness of the dielectric welding film is in a range
from 10 to 2000 .mu.m. The bonding method includes the following
steps (1) and (2):
(1) holding the dielectric welding film between a plurality of
adherends of the same material or different materials; and (2)
applying dielectric heating on the dielectric welding film held
between the plurality of adherends with a dielectric heater at a
high-frequency output ranging from 0.1 to 20 kW for a
high-frequency-wave application time of 1 second or more and less
than 40 seconds.
[0122] The bonding method of the dielectric welding film according
to the second exemplary embodiment will be described below mainly
on features different from those in the first exemplary
embodiment.
1. Step (1)
[0123] In the step (1), the dielectric welding film is disposed at
a predetermined position, where the dielectric welding film is held
between the plurality of adherends of the same material or
different materials.
[0124] At this time, it is usually preferable to hold the
dielectric welding film between the plurality of adherends after
the dielectric welding film is cut into pieces of a predetermined
shape.
[0125] Moreover, it is also preferable, in order to locate the
dielectric welding film at a correct position without position gap,
to provide a sticky portion all over or on a part of one side or
both sides of the dielectric welding film and/or to provide a
temporary fixing hole or projection on a part of the dielectric
welding film.
[0126] The material of the adherend used in the second exemplary
embodiment is not specifically limited but may be any one of an
organic material, an inorganic material or a metal material or a
composite of the organic, inorganic and metal materials. Examples
of the organic material include a plastic material such as
polypropylene resin, polyethylene resin,
acrylonitrile-butadiene-styrene copolymer resin (ABS resin),
polycarbonate resin, polyamide resin (e.g. Nylon 6, Nylon 66),
polybutylene terephthalate resin (PBT resin), polyacetal resin (POM
resin), polymethyl methacrylate resin and polystyrene resin, and a
rubber material such as styrene-butadiene rubber (SBR), ethylene
propylene rubber (EPR) and silicone rubber. Examples of the organic
material include glass. A fiber-reinforced resin (FRP), which is a
composite of glass fiber and the above plastic material, is also
preferable as the material of the adherend.
[0127] In particular, the dielectric welding method of the second
exemplary embodiment, which achieves tight bonding, is suitably
applicable to an instance in which at least one of the adherends is
made of a material of poor adhesiveness (e.g. polypropylene and
polyethylene) due to its low polarity.
2. Step (2)
[0128] In the step (2), dielectric heating is applied on the
dielectric welding film held between the plurality of adherends
with a dielectric heater, for instance, at a high-frequency output
ranging from 0.1 to 20 kW for a high-frequency-wave application
time ranging from 1 to 40 seconds, as shown in FIG. 5.
[0129] The dielectric welding machine used in the step (2) and
dielectric heating conditions thereof will be described below.
(1) Dielectric Welding Machine
[0130] As shown in FIG. 5, a dielectric welding machine 10 performs
dielectric heating through a dielectric welding film 13 held
between a first adherend 12 and a second adherend 14 and applies
pressure by a first high-frequency electrode 16 and a second
high-frequency electrode 18 to bond the first adherend 12 and the
second adherend 14.
[0131] The dielectric welding machine 10 includes a high-frequency
power source 20 configured to apply a high-frequency wave of, for
instance, approximately 28 MHz or 40 MHz to each of the oppositely
disposed first high-frequency electrode 16 and second
high-frequency electrode 18.
[0132] When a high-frequency electric field is created between the
electrodes, high-frequency wave energy is absorbed by the
dielectric welding film (more specifically, a dielectric heating
medium uniformly dispersed in the dielectric welding film) at a
part at which the first adherend and the second adherend are
overlapped.
[0133] The dielectric heating medium serves as a heat source, the
heat generated by the dielectric heating medium melting the olefin
resin (i.e. the main component of the dielectric welding film) and
thereby bonding the first adherend and the second adherend.
[0134] Subsequently, compression force is applied by the first
high-frequency electrode 16 and the second high-frequency electrode
18 serving also as a press machine as shown in FIG. 5. The melting
of the dielectric welding film 13 in combination with the
compression force applied by the electrodes 16 and 18 achieves
tight welding of the first adherend 12 and the second adherend
14.
(2) Dielectric Heating Conditions
[0135] Though the dielectric heating conditions can be altered as
desired, the high-frequency output is usually preferably in a range
from 0.1 to 20 kW, more preferably in a range from 0.2 to 10 kW,
further preferably in a range from 0.2 to 5 kW.
[0136] The application time of the high-frequency wave is
preferably in a range from 1 to 40 seconds, more preferably in a
range from 5 to 30 seconds, further preferably in a range from 10
to 20 seconds.
[0137] The frequency of the high-frequency wave is preferably in a
range from 1 to 100 MHz, more preferably in a range from 5 to 80
MHz, further preferably in a range from 10 to 50 MHz. Specifically,
13.56 MHz, 27.12 MHz, and 40.68 MHz of ISM band allocated by the
International Telecommunication Union are used for the dielectric
welding method according to the second exemplary embodiment.
EXAMPLES
Example 1
1. Preparation of Dielectric Welding Film
[0138] 100 parts by weight of a polypropylene resin (NOVATEC PPMH4
manufactured by Japan Polypropylene Corporation, polypropylene
homopolymer, melting point: 165 degrees C., referred to as A1 in
Table 1) as the (A) component, and 69 parts by weight of zinc oxide
(LPZINC11 manufactured by Sakai Chemical Industry Co., Ltd., mean
particle size: 11 .mu.m, referred to as B1 in Table 1) as the (B)
component were each weighed for preparation.
[0139] Subsequently, as shown in Table 1, the (A) component and (B)
component were preliminarily blended and then were fed into a
hopper of a biaxial extruder of 30 mm diameter, where the
components were melted and kneaded at a cylinder set temperature in
a range from 180 to 200 degrees C. and a die temperature of 200
degrees C. to obtain granular pellets.
[0140] Then, the obtained granular pellets were put into a hopper
of a uniaxial extruder provided with a T-die, and a 400-.mu.m thick
film-shaped molten kneaded product was extruded from the T-die at a
cylinder temperature of 200 degrees C. and a die temperature of 200
degrees C., and cooled to a room temperature to obtain the
dielectric welding film of Example 1.
[0141] A surface of the dielectric welding film and a cross section
of the dielectric welding film are shown in photographs
(1000.times. magnification) in FIGS. 6 (a) and (b),
respectively.
2 Evaluation of Dielectric Welding Film
(1) Thickness
[0142] Thicknesses of the obtained dielectric welding film were
measured at 10 spots with a micrometer and an average of the
thicknesses was calculated.
(2) Total Light Transmissivity
[0143] The total light transmissivity was measured in accordance
with JIS K 7361-1 (1997) with a haze meter NDH5000 manufactured by
NIPPON DENSHOKU INDUSTRIES CO., LTD. under Illuminant D65.
(3) Dielectric Property (Tan .delta./.epsilon.')
[0144] With a material analyzer E4991 (manufactured by Agilent
Technologies, Inc.), the permittivity E' and dissipation factor tan
.delta. of the welding film were measured at 23 degrees C. and 40
MHz frequency to calculate the value of (tan
.delta./.epsilon.').
(4) Storage Modulus E'
[0145] Storage modulus E' of the welding film cut into a strip of
15 mm.times.5 mm.times.1 mm was measured with a dynamic
viscoelasticity measuring machine (Q-800 manufactured by TA
Instruments).
[0146] Specifically, viscoelasticity measurement was performed in a
tensile mode at 10 Hz frequency, at temperature-increase rate of 3
degrees C./min and in a measurement temperature range of -100 to
200 degrees. The storage modulus E' was measured at predetermined
temperatures (normal temperature (23 degrees C.) and 80 degrees
C.).
(5) High-Frequency Weldability
[0147] A dielectric welding film (welding film) cut into a 25
cm.times.12.5 cm piece was held at a predetermined position between
two glass-reinforced polypropylene plates (25 cm.times.10
cm.times.1.5 mm) as adherends.
[0148] Subsequently, while the plates were held between electrodes
of a high-frequency dielectric heater (YRP-400T-A manufactured by
YAMAMOTO VINITA CO., LTD), a high-frequency wave of 40 MHz
frequency and 200 W output was applied for a predetermined time to
prepare a test piece (i.e. adherends bonded through the welding
film).
[0149] High-frequency weldability of the obtained test piece was
evaluated according to the standards below.
.circleincircle.: The adherends were bonded through the welding
film by applying the high-frequency wave for less than 10 seconds.
.largecircle.: The adherends were bonded through the welding film
by applying the high-frequency wave for a time period of 10 seconds
or more and less than 40 seconds. .DELTA.: The adherends were
bonded through the welding film by applying the high-frequency wave
for a time period of 40 seconds or more and less than 60 seconds.
x: The adherends were not bonded through the welding film even
after applying the high-frequency wave for 60 seconds.
(6) Tensile Shear Test
[0150] With a universal tensile tester (Instron 5581 manufactured
by Instron Corporation), a tensile shear force of the test piece
obtained in the evaluation in "(5) High-Frequency Weldability" was
measured at a tension rate of 100 mm/min, and was observed in terms
of destroy mode.
.circleincircle.: Material failure or cohesive failure occurred and
the tensile shear strength was 6 MPa or more. .largecircle.:
Material failure or cohesive failure occurred and the tensile shear
strength was 2 MPa or more and less than 6 MPa. .DELTA.:
Interfacial peeling occurred and the tensile shear strength was
less than 2 MPa. x: The test piece was not welded in the evaluation
of the high-frequency weldability, or the weld could not be kept
until the test (i.e. the adherend was dropped off), so that the
tensile shear test was not available.
(7) High-Temperature Creep Test
[0151] After a 100-gram weight was attached to an end of the test
piece obtained in the evaluation of "(5) High-Frequency
Weldability," the test piece was placed in an oven at 80 degrees C.
with the weight being suspended therefrom, and was left still for
24 hours.
[0152] Lastly, the test piece, after taken out of the oven and
returned to a room temperature, was evaluated in terms of the
high-temperature creep according to the standards below.
.circleincircle.: The weight was kept attached after the elapse of
24 hours. .largecircle.: Though kept attached until an elapse of 12
hours, the weight was dropped after the elapse of 24 hours.
.DELTA.: The weight was dropped off within 12 hours. x: The test
piece was not welded in the evaluation of the high-frequency
weldability, or the weld could not be kept until the test (i.e. the
adherend was dropped off), so that the high-temperature creep test
was not available.
Example 2
[0153] In Example 2, a dielectric welding film was prepared and
evaluated in the same manner as in Example 1 except that the
content of the (B) component was slightly reduced (156 parts by
weight with respect to 100 parts by weight of the (A)
component).
Example 3
[0154] In Example 3, a dielectric welding film was prepared and
evaluated in the same manner as in Example 1 except that the
content of the (B) component was further reduced (267 parts by
weight with respect to 100 parts by weight of the (A)
component).
Example 4
[0155] In Example 4, a dielectric welding film was prepared and
evaluated in the same manner as in Example 1 except that the type
of zinc oxide as the (B) component was changed from B1 to B2
(LPZINC2 manufactured by Sakai Chemical Industry Co., Ltd.,
amorphous, mean particle size 2 .mu.m, referred to as B2 in Table
1) and the content of the (B) component was 156 parts by weight
with respect to 100 parts by weight of the (A) component.
Example 5
[0156] In Example 5, a dielectric welding film was prepared and
evaluated in the same manner as in Example 1 except that the type
of zinc oxide as the (B) component was changed from B1 to B3
(LPZINC20 manufactured by Sakai Chemical Industry Co., Ltd.,
amorphous, mean particle size: 20 .mu.m, referred to as B3 in Table
1) and the content of the (B) component was 156 parts by weight
with respect to 100 parts by weight of the (A) component.
Example 6
[0157] In Example 6, the dielectric welding film was prepared and
evaluated in the same manner as in Example 1 except that random
polypropylene (Prime Polypro F-744NP manufactured by Prime Polymer
Co., Ltd., melting point: 130 degrees C., referred to as A2 in
Table 1) was used as the (A) component, and the content of the (B)
component was 156 parts by weight with respect to 100 parts by
weight of the (A) component.
Example 7
[0158] In Example 7, a dielectric welding film was prepared and
evaluated in the same manner as in Example 1 except that
ethylene-.alpha.-olefin copolymer (EXCELLEN FX352 manufactured by
SUMITOMO CHEMICAL Co., Ltd., melting point: 70 degrees C., referred
to as A3 in Table 1) was used as the (A) component, and the content
of the (B) component was 69 parts by weight with respect to 100
parts by weight of the (A) component.
Comparative 1
[0159] In Comparative 1, a dielectric welding film was prepared and
evaluated in the same manner as in Example 1 except that the type
of zinc oxide as the (B) component was changed from B1 to B4 (zinc
oxide special grade, manufactured by Wako Pure Chemical Industries
Ltd., amorphous, mean particle size: 0.4 .mu.m, referred to as B4
in Table 1) and the content of the (B) component was 69 parts by
weight with respect to 100 parts by weight of the (A)
component.
Comparative 2
[0160] In Comparative 2, a dielectric welding film was prepared and
evaluated in the same manner as in Example 1 except that the type
of zinc oxide as the (B) component was changed from B1 to B5
(LPZINC-S50 manufactured by Sakai Chemical Industry Co., Ltd.,
spherical, mean particle size: 50 .mu.m, referred to as B5 in Table
1) and the content of the (B) component was 69 parts by weight with
respect to 100 parts by weight of the (A) component.
TABLE-US-00002 TABLE 1 Examples 1 2 3 4 5 Resin Composition (A)
Component Type A1 A1 A1 A1 A1 homo poly- homo poly- homo poly- homo
poly- homo poly- propylene propylene propylene propylene propylene
Melting point (.degree. C.) 165 165 165 165 165 MFR (g/10 min) 5 5
5 5 5 Parts by weight 100 100 100 100 100 (B) Component Type B1 B1
B1 B2 B3 zinc oxide zinc oxide zinc oxide zinc oxide zinc oxide
Particles size (.mu.m) 11 11 11 2 20 Parts by waight 69 156 267 156
156 Evaluation of Thickness (.mu.m) 400 400 400 400 400 Welding
Film Total light transmissivity (%) 29 23 19 9 35 dielectric
property (tan.delta./.epsilon.') 0.008 0.016 0.028 0.008 0.008
Storage modulus E' (23.degree. C.) (MPa) 2,370 2,450 2,710 2,180
2,650 Storage modulus E' (80.degree. C.) (MPa) 540 560 600 530 590
High-frequency dielectric weldability .largecircle. .largecircle.
.circleincircle. .largecircle. .largecircle. Tensile shear test
.circleincircle. .circleincircle. .circleincircle. .circleincircle.
.circleincircle. High-temperature creep resistance .circleincircle.
.circleincircle. .circleincircle. .circleincircle. .circleincircle.
Examples Comparatives 6 7 1 2 Resin Composition (A) Component Type
A2 A3 A1 A1 random ethylene/.alpha.- homo poly- homo poly- poly-
olefin propylene propylene propylene copolymer Melting point
(.degree. C.) 130 70 165 165 MFR (g/10 min) 7 4 5 5 Parts by weight
100 100 100 100 (B) Component Type B1 B1 B4 B5 zinc oxide zinc
oxide zinc oxide zinc oxide Particles size (.mu.m) 11 11 0.4 50
Parts by waight 156 69 69 69 Evaluation of Thickness (.mu.m) 400
400 400 400 Welding Film Total light transmissivity (%) 24 27 2 40
dielectric property (tan.delta./.epsilon.') 0.016 0.008 0.002 0.002
Storage modulus E' (23.degree. C.) (MPa) 1,320 160 2,380 2,320
Storage modulus E' (80.degree. C.) (MPa) 270 0.4 540 540
High-frequency dielectric weldability .largecircle. .largecircle.
.DELTA. X Tensile shear test .circleincircle. .circleincircle. X X
High-temperature creep resistance .circleincircle. X X X
INDUSTRIAL APPLICABILITY
[0161] With the use of the dielectric welding film according to the
exemplary embodiments of the invention, adherends, which are made
of hydrocarbon-based non-polar thermoplastic resin (e.g. polyolefin
resin) and usually hard to bond even with the use of a solvent or a
proper adhesive, can be tightly bonded through the dielectric
heating within a short time of less than 40 seconds.
[0162] Since the bonding portion can be selectively heated and
melted from an outside and adherends in a form of three-dimensional
components can be bonded through the dielectric heating, it is
expected that this dielectric welding process is utilized for
producing large-sized components and/or components with complicated
structures.
[0163] Specifically, the invention, in which a predetermined
welding portion is heated from an outside through the dielectric
heating, is suitable for bonding thick components,
three-dimensional components and components with small acceptable
tolerance.
[0164] In particular, since the invention allows local application
to a bonding portion of adherends, the invention is expectable to
be effective in bonding large-sized and complicated
three-dimensional structures, laminated structures, and the
like.
[0165] Accordingly, the invention allows highly tightly welding of
polyolefin-resin adherends, and is applicable to a high-performance
thermoplastic resin composite such as fiber-reinforced plastics
(FRP), which is expected to be increasingly widely used in the time
to come.
[0166] Further, the invention allows relatively easy control of
physical properties such as the thickness and storage modulus of
the welding film, and thus is applicable to a roll-to-roll process.
Further, the dielectric welding film can be designed into any size
and shape by punching or the like depending on the adhesion area
and shape between the plurality of adherends.
[0167] In addition, the invention is expected to be used as a
bonding technology for bonding fiber-reinforced plastics (FRP) in
the fields of airplane and automobile whose weight is increasingly
reduced, and for bonding components of electronics and medical
equipment whose size is increasingly reduced and structure is
increasingly complicated.
[0168] In this regard, polyolefin resin such as polyethylene and
polypropylene, which is inferior in solvent resistance, is hard to
bond with an adhesive diluted with solvent. Meanwhile, a mechanical
connector such as a bolt and a rivet for bonding polyolefin resin
increases the weight of the component and may be inferior in the
strength of the bonded portion.
[0169] According to the invention, the polyolefin resin and the
like can be stably and tightly bonded without increasing weight of
the component.
EXPLANATION OF CODES
[0170] 10: high-frequency dielectric heater [0171] 12: first
adherend [0172] 13: dielectric welding film [0173] 14: second
adherend [0174] 16: first high-frequency electrode (also serving as
a part of a press machine) [0175] 18: second high-frequency
electrode (also serving as a part of a press machine) [0176] 20:
high-frequency power source
* * * * *